Experiment #5 Molecular Fluorescence Laboratory Experiment (Two-week, 200 pts experiment) The Determination of Quinine i

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Experiment 5 Molecular Fluorescence Laboratory Experiment Two Week 200 Pts Experiment The Determination Of Quinine I 1 (78.17 KiB) Viewed 32 times

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Experiment #5 Molecular Fluorescence Laboratory Experiment (Two-week, 200 pts experiment) The Determination of Quinine in Beverages Determination of Quinine concentration in ppm (part per million) in several brand name Tonic Water Prelab Questions In addition to the experimental results, graphs, and calculations your report should include: A. What is Quinine? B. What is the molecular formula and molecular structure of Quinine? C. What are the different applications, medical and nonmedical, of Quinine? D. What is the medical concentration of Quinine and what is its concentration limit in soft drinks? Search the internet to give complete answers for the above questions (A-D) Discussion Quinine solutions fluoresce strongly when excited by radiation at 350 nm. The relative intensity of the fluorescence peak at 450 nm provides a sensitive method for the determination of quinine in beverages. Preliminary measurements are needed to define a concentration region in which fluorescence intensity is either linear or nearly so. The unknown is then diluted as necessary to produce readings within this range. PREPARATION OF REAGENTS 1. Sulfuric acid. 0.05 M. Add about 17 mL of 6 M H2SO4 to 2.0 L of distilled water. 2. Quinine sulfate standard solutions: Follow the dilution process to prepare the standard quinine solutions in the required ppm range PROCEDURE Determination of a Suitable Concentration Range (This part is already done for you in the experiment set up) Use the SHIMADZU Spectrofluorometer Model RE5301 PC located in room ME 718 Solutions are measured in a 10.0 mm quartz fluorescence cell Set the fluorometer for a 350 nm excitation wavelength. To find a suitable working range, measure the relative fluorescence intensity of the 1-ppm standard at an emission wavelength of 450 nm. Use a graduate cylinder to dilute 10 mL of the 1-ppm solution with 10 mL of 0.05 M H2SO4, again measure the relative fluorescence. Repeat this dilution and measurement process until the relative intensity approaches that of a blank consisting of 0.05 M H2SO4. Make a plot of the data, and select a suitable range for the analysis (that is, a region within which the plot is linear). Preparation of a Calibration Curve Use volumetric glassware to prepare five standards solutions that span the linear region (0.00, 1.00, 2.00, 3.00, 4.00 and 5.00 ppm); measure the fluorescence intensity for each. Construct the calibration curve FL intensity vs. Quinine concentration in ppm.
Analysis Obtain an unknown (Tonic Water). Make suitable dilutions with 0.05 M H2SO4 to bring its fluorescence intensity within the calibration range (1 to 25 dilution). Determine the concentration of quinine in the unknown Tonic water in parts per million (ppm) Preparation of standard Quinine sulfate solution: 1- Quinine sulfate is not freely soluble in pure water, thus all measurements are done in 0.05 M H2SO4 2. Quinine concentration in Tonic Water is in the range of tens ppm (part per million i.e. 1/1000,000). 3- Prepare about 2.0 L solution of 0.05 M H2SO4 to be used as a solvent for the entire experiment. 4- Weigh out 0.1250 g (to the nearest 0.5 mg, i.e. 0.1250 = 0.0005) quinine sulfate on weighing paper. 5. In a 500 ml volumetric flask, dissolve the solid completely in small amount of 0.05 M H2SO4 When completely dissolved complete the volume to the mark. 6- Shake solution and label the flask. 7- Calculate the solution concentration in ppm (part per million) and print concentration on label. 8. Measure the following volumes of this solution in 25 ml measuring flasks: (1) 100 ML, (ii) 200 L, (iii) 300 , (iv) 400 pl., and (v) 500 pl. 9- Dilute each solution with 0.05 M H:SO and complete to the mark. 10- Shake solutions and label cach flask 11- Calculate the concentration (in ppm) of the resulting standard quinine sulfate solutions and print the concentration on each label. Now, you prepared 5 standard solutions of quinine sulfate with known ppm concentrations in addition to a 0.0 ppm quinine sulfate solution as a blank (that is pure 0.05 M H:SO4 solution with no quinine sulfate added) Spectrofluorometric parameters Fluorescence measurement for both the standard and unknown Tonic Water solutions are measured using th following instrumental set-up Instrument: SHIMADZU Spectrofluorometer - Model RE5301PC (in room ME718) Excitation wavelength: Emission wavelength: Excitation slit width: Emission slit width: Instrument sensitivity: Scan speed: Emission is measured in 10 mm Fluorescence Quartz cells Use Excel software to plot a calibration curve between the standard quinine concentration in ppm (X-axis) and the Fluorescence intensity (Y-axis). From the graph determine the linear relation equation between Fluorescence and ppm concentration. [Graph should data points for 5 standards + a blank solution] Tonic Water Analysis (Unknowns): Prepare diluted Tonic Water in 25 mL measuring flasks using for 0.05 M H:SO. (Dilution is 1.0 mL Tonic Water diluted to 25 mL) [You must consider this dilution factor when calculating the original quinine concentration in Tonic Water] Measure the fluorescence of each solution of the unknown tonic water sample. Tabulate your data and calculate the quinine concentration in each unknown using the resulting straight line equation obtained from the calibration curve.
Your report must include: (1) Detailed literature search report on quinine including: (i) molecular formula and structure, (ii) the medical and nonmedical applications of quinine and its concentration range in each application and (iii) the quantitative methods for the determination of quinine concentration. (2) A Complete Calibration curve (Table 1 data sheet). The calibration curve must include: graph title, labeled axes with units in correct SF, linear (trendline) equation relating fluorescence intensity and quinine concentration, and the correlation factor "R?". (3) A Completed Table 2, listing your findings and the calculated concentration of quinine in your unknowns (Different brand name Tonic Water). (4) Complete calculation sheet with all calculation steps. Apply significant figures rules and showing correct units for all measurements. (5) Your conclusion
Quinine Cone BLANK (OPPM 1 PPM GroupLA 0033 17.956 32 649 50.777 65.815 IGIOUP R B Group C 0.033 0.033 19 Nog 16. 37| 37.438 34.618 53.235 49,031 68.996 V UNKNOWNS 2 PPM 3 PPM 4 PPM 67.749 5PP 83.224 85.737 182527 1. Canada dry 39,120. 39.200 2. vintage tonic 138.161 v 3. Diet vintage 127.195 | 27.1871 26.934 H. Schweppes s. Schweppes Diet ul 38.727 u 31.257 35.576 v TE